The present invention relates to high molecular weight alternating and random block copolymers and methods for their preparation; more particularly, the present invention relates to high molecular weight carborane-siloxane alternating and random block copolymers with high performance rigid materials, and methods for their preparation.
Carborane-siloxane polymers are known in the art; see, for example, an article entitled "Carboranesiloxane Polymers" by H. A. Schroeder in Rubber Age, February 1969 and U.S. Pat. No. 3,689,455. These polymers have excellent high temperature properties and are generally superior in this respect to the silicone and fluorocarbon rubbers. The polymers may be compounded with suitable fillers and additives and fabricated into cured elastomeric articles. The excellent high temperature properties of such elastomers make them especially useful for a wide variety of applications, such as gaskets, seals, wire and cable insulation, and the like. Linear, high molecular weight carborane-siloxane polymers and methods for their preparation are disclosed in commonly-assigned, copending U.S. patent application Ser. No. 770,509, filed Feb. 22, 1977.
High performance rigid polymers are known which exhibit excellent mechanical performance and in some cases solvent resistance. Examples of such polymers are polysulfones, polyimides, polyarylethers, aromatic and alkyl polyesters, polyphenylene sulfides, polyquinoxalenes, polybenzimidizoles, and the like. Typically, these high performance polymers are linear thermoplastic, stiff or rigid polymers characterized by high phase transition and high tensile and flexural modulus values.
Block copolymer elastomers, i.e. copolymers formed by joining two separate polymer chains of different materials which have either been previously separately polymerized or copolymerized together, are known in the art. Such block copolymer elastomers, as compared to their vulcanized counterparts, have certain advantages which include their greater versatility, the ease of processing and potential for reuse of scrap and excellent mechanical properties. For example, polyarylene polyether block copolymers with organopolysiloxanes and lactams are disclosed in U.S. Pat. Nos. 3,536,657, 3,539,665, 3,539,656, 3,539,657 and 3,657,385. Polysulfonepolydimethylsiloxane block copolymers are disclosed in an article by A. Noshay et al., Polymer Reprints 12, 1 (1971) 247.
Elastomeric block copolymers have now been developed which combine the elastomeric capabilities of carborane-siloxane elastomers with the mechanical performance and solvent resistance of high performance rigid materials without compromising the thermal capabilities of either system. Through the proper selection of the rigid block and the elastomeric carborane-siloxane block, copolymers are provided which possess both the advantages normally associated with thermoplastics (e.g., short fabrication cycles, reprocessability, etc.) and those normally associated with carborane-siloxane polymers (e.g., thermal stability and elastomeric behavior over a wide temperature range, etc.). The block copolymers of the invention are useful in high temperature applications as gaskets, seals, wire and cable insulation, and the like.